This invention relates to functional color graphic printing and more particularly to the use of Travelling Cloud Development (T.C.D.) for developing lonographically formed latent images.
Of the various electrostatic printing techniques, the most familiar is that of xerography wherein latent electrostatic images formed on a charge retentive surface are developed by a suitable toner material to render the images visible, the images being subsequently transferred to plain paper.
A less familiar form of electrostatic printing uses ions deposited on an electroreceptor. In ionographic devices such as that described in U.S. Pat. No. 4,524,371 granted to Sheridon et al. or U.S. Pat. No. 4,463,363 granted to Gundlach et al., an ion producing device generates ions to be directed past a plurality of modulation electrodes to an imaging surface. In one type of ionographic device, ions are produced at a coronode supported within an ion chamber, and a moving fluid stream entrains and carries ions produced at the coronode out of the chamber. At the chamber exit, a plurality of control electrodes or nibs are modulated with a control voltage to selectively control passage of ions through the chamber exit. Ions directed through the chamber exit are deposited on a charge retentive surface in imagewise configuration to form an electrostatic latent image developable by electrostatographic techniques for subsequent transfer to a final substrate. The arrangement produces a high resolution non-contact printing system. Other ionographic devices exist which operate similarly, but do not rely on a moving fluid stream to carry ions to a surface.
U.S. Pat. No. 4,879,194 granted to Christopher Snelling discloses a method and apparatus using ion projection to form a tri-level latent image on a charge retentive surface. The tri-level image described therein comprises two image areas and a background area, the former of which are developed using magnetic brush development.
U.S. Pat. No. 4,647,179 granted to Fred W. Schmidlin discloses toner transporting apparatus for use in developing powder images on an imaging surface such a photoconductive belt. The apparatus is characterized by the provision of a travelling electrostatic wave conveyor for transporting toner particles from a supply of toner to the imaging surface. The conveyor comprises a linear electrode array consisting of spaced apart electrodes to which a multiphase AC voltage is connected such that adjacent electrodes have phase shifted voltages applied thereto which cooperate to form a travelling wave.
U.S. Pat. No. 4,731,634 granted to Howard M. Stark discloses a method and apparatus for rendering latent electrostatic images visible using multiple colors of dry toner or developer for developing black and at least two highlight color images in a single pass of the imaging surface through the development stations of the apparatus. Two of the toners are attracted to only one charge level on the charge retentive surface to form the black and one highlight color image and two toners are attracted to a third image level to form the second highlight color.
U.S. Pat. No. 4,660,059 granted to John F. O'Brien discloses an apparatus in which a document is printed in at least two different colors. Ions are projected onto the surface of a receiving member to record at least two electrostatic latent images thereon. Each of the electrostatic latent images recorded on the receiving member is developed with different color marking particles. The different color marking particles are transferred substantially simultaneously from the receiving member to the document to print the desired information thereon.